The Sims 2 won't uninstall

My grandaughter has The Sims 2 Game on her computer and wants to remove it. she has clicked on uninstall on the the game but it doesn't! she has also tried to remove it from add&remove in control panel but this doesn't work either. she installed Unlocker from the net and updated it but the programme doesn't seem to be working. Has anyone any idea how to get rid of it please its using quite a bit of disc space. she has XP Professional 64 bit